Why does the value change on scroll?

[waverider]

SetBarsRequired(sbrAll);
_SECTION_BEGIN("Price");

SetChartOptions(0,chartShowArrows|chartShowDates|chartWrapTitle);
_N(Title = StrFormat("{{NAME}} - {{INTERVAL}} {{DATE}} Open %g, Hi %g, Lo %g, Close %g (%.1f%%), FCD %g {{VALUES}} ", O, H, L, C, SelectedValue( ROC( C, 1 ))/*, futureCloudDirection */) );
Plot( C, "Close", ParamColor("Color", colorDefault ), styleNoTitle | ParamStyle("Style") | GetPriceStyle(), Null, Null, 0, 1, 1);

_SECTION_END();
_TRACE("Close="+C[100]);
_TRACE("Close="+Ref(C, -1));

When you scroll the chart the close value printed in 2nd trace command changes. So signals that use Ref(C, -1) also disappear/reappear on scroll. is there a workaround? my code does not use loops and i would like to keep it that way.